Reproducing device, reproducing method and audio data storage medium

ABSTRACT

In order to provide an audio device capable of making more effective use of non-compressed audio data and compressed audio data, according to the present invention, compressed audio data as computer data is stored in a data track in a Mixed-mode CD. By allowing a playback apparatus to recognize the presence of the compressed audio data, both the compressed audio data and non-compressed audio data stored in a CD-DA track are played back.

TECHNICAL FIELD

The present invention relates to a playback apparatus for audio data,and more particularly, to an apparatus capable of playing back an audiodata storage medium having a mixture of non-compressed audio data andcompressed audio data.

BACKGROUND ART

Presently, the most popular standard or medium for storing audio data isCD-DA (CD-Digital Audio). In CD-DA, a 74-minute digital signal can berecorded on a disk having a diameter of 12 cm. Recently, however, audiodata compression techniques such as MP3 (MPEG-1 Audio Layer-III), ATRAC3(Adaptive Transform Acoustic Coding 3), and WMA (Windows Media Audio)have been developed, and more and more users have enjoyed music on theircomputers using audio data which has been compressed by such compressiontechniques. Such compression techniques have features to compress thecapacity of CD-DA audio data to, for example, about 1/10, and to providelow degradation in sound quality. In terms of the recording time ofmusic, CD-DA non-compressed audio data is limited to a capacity of about74 minutes per disk, while compressed audio data can have a capacity ofover 700 minutes per disk. The compressed audio data can be written to,for example, a Recordable CD (Recordable Compact Disc), and audiodevices capable of playing back Recordable CDs having compressed audiodata written thereto have been marketed.

As described above, when users enjoy music, she/he can usenon-compressed audio data and compressed audio data. It is an object ofthe present invention to provide an audio device capable of making moreeffective use of non-compressed audio data and compressed audio data.

DISCLOSURE OF INVENTION

It is possible to write both CD-DA audio data files and data files inanother format. In disks of this type, two formats, namely, Mixed-modeCD and Enhanced CD (also called CD-Extra) are currently available.

The Mixed-mode CD refers to a CD (Compact Disc) having a data track andan audio track stored on a single medium. More specifically, as shown inFIG. 6, a data track and a CD-DA track are written, in this order, in asingle session. As used herein, data track refers to a track regionhaving data in a computer-processible format (computer data) storedthereon, and CD-DA track refers to a track region having CD-DAnon-compressed audio data stored thereon. The Mixed-mode CD is oftenused for software games, etc. In this case, a game program is written onthe data track, and background music for the game is written on theCD-DA track. Basically, the Mixed-mode CD is a standard for personalcomputers. Thus, if the disk is played back on an audio CD player, nosound or loud noise sound is produced from the data track portion. If itis to be played back on a CD-ROM player for a personal computer, on theother hand, the CD-ROM player only recognizes the data track, but doesnot read the data on the CD-DA track.

The Enhanced CD includes first and second, that is, two, sessions; thefirst session has a CD-DA track written therein and the second sessionhas a data track written therein. The second session is stored in a modecapable of recording moving pictures, images, and programs. In mostcases, video clips, picture albums, mini-games, screen savers, etc., arerecorded in the second session. If this disk is played back on a musicCD player, the music CD player can only recognize the CD-DA track in thefirst session, thus causing only the CD-DA track on the innercircumference to be played back as a CD-DA disk. Therefore, the problemof producing noise does not occur. When it is to be played back on aCD-ROM player for a personal computer, on the other hand, the CD-ROMplayer recognizes and processes only the data track in the secondsession.

It would be more beneficial to users to write two kinds of data, namely,CD-DA non-compressed audio data and compressed audio data, on a singledisk and to play back this disk on a single audio device. As describedabove, in the conventional art, disks capable of having both CD-DA audiodata files and data files in other formats written thereon areavailable, and it is possible to write CD-DA audio data and compressedaudio data to a single disk, such as a Recordable CD. By doing so, anovel music medium having music sensitive to sound quality written asCD-DA audio data and music otherwise written as compressed audio datacan be achieved.

Audio devices capable of playing back compressed audio data have beenavailable heretofore. When a disk is inserted therein, the audio devicecan recognize that the disk is either a CD-DA disk or a compressed audiodata, for example, MP3, disk and can play back the disk. However, theaudio device does not assume that a mixture of CD-DA audio data andcompressed audio data is written on a single disk. That is, the audiodevice cannot play back a disk having a mixture of CD-DA audio data andcompressed audio data written thereon to play back both the CD-DA audiodata and the compressed audio data. Accordingly, the present inventionprovides a medium having a mixture of non-compressed audio data such asCD-DA and compressed audio data as computer data, and also provides aplayback apparatus capable of playing back both the non-compressed audiodata and the compressed audio data on such a medium.

Specifically, the present invention provides a playback apparatus forplaying back a medium having audio data stored thereon, including: adetermining unit for determining if a predetermined medium receivedtherein contains a mixture of compressed audio data and non-compressedaudio data; and a playback mechanism for playing back the compressedaudio data and the non-compressed audio data, which are stored in themedium, based on the determination result of the determining unit.

In the playback apparatus according to the present invention, thecompressed audio data can have a computer data format.

The playback apparatus according to the present invention can determineif it contains a mixture of compressed audio data and non-compressedaudio data, and can play back the audio data according to thatdetermination result, thereby allowing a medium having a mixture ofcompressed audio data and non-compressed audio data to be played backwithout changing the medium.

Whereas, an audio device in the conventional art does not presume thatcompressed audio data and non-compressed audio data are mixed in asingle disk, and cannot determine the mixture.

In the playback apparatus according to the present invention, if thepredetermined medium received in the playback apparatus includes asession formed of a lead-in, a data storage area, and a lead-out, thedetermining unit should determine if compressed audio data andnon-compressed audio data are mixed in the data storage area in thesession. In a Mixed-mode CD in the state of the art, a data track and aCD-DA track are written, in this order, in a single session. Thus, byrecognizing that the predetermined medium is a Mixed-mode CD, and thatcompressed audio data is present in the data track, it is possible todetermine that compressed audio data and non-compressed audio data aremixed in the data storage medium in the session.

In the playback apparatus according to the present invention, if thepredetermined medium received in the playback apparatus includes atleast two sessions each formed of a lead-in, a data storage area, and alead-out, the determining unit should determine if compressed audio datais stored in the data storage area in one session of the two sessionsand if non-compressed audio data is stored in the data storage area inthe other session. In an Enhanced CD in the state of the art, asdescribed above, a CD-DA track is written in a first session, and a datatrack is written in a second session. Thus, by recognizing that thepredetermined medium has two sessions, and that compressed audio data ispresent in the second session, it is possible to determine that it is amedium having a mixture of compressed audio data and non-compressedaudio data.

Furthermore, the playback apparatus according to the present inventioncan play back a medium having only CD-DA data stored thereon or a mediumhaving only compressed audio data stored thereon if the determining unitdetermines whether only either compressed audio data or non-compressedaudio data is stored in the data storage area in the session.

As known in the art, session as used herein refers to a unit of a regionhaving a group of three storage portions consisting of a lead-in, a datastorage area, and a lead-out, in which the lead-in at least includesinformation on the storage position of data, and the lead-out includesinformation indicating the end portion of the session. The concept ofthe session, the lead-in, and the lead-out in the present inventiontakes after the concept known in the art.

The present invention further provides a playback apparatus for playingback a medium having audio data stored thereon, including: a playbackmechanism including a compressed audio data playback mode and anon-compressed audio data playback mode; a determining unit fordetermining whether one or both of non-compressed audio data andcompressed audio data are stored in a predetermined medium receivedtherein; and a control unit for selecting a playback mode in theplayback mechanism based on the determination result of the determiningunit, wherein the control unit selects the non-compressed audio dataplayback mode if the determining unit determines that onlynon-compressed audio data is stored as audio data in the predeterminedmedium, selects the compressed audio data playback mode if thedetermining unit determines that only compressed audio data is stored asaudio data in the predetermined medium, and selects both the compressedaudio data playback mode and the non-compressed audio data playback modeif the determining unit determines that both non-compressed audio dataand compressed audio data are stored in the predetermined medium.

This playback apparatus determines what audio data is stored in themedium, and selects the playback mode according to the determinationresult, thereby allowing a user to enjoy music without worrying aboutthe format of the medium. In addition, a medium having both compressedaudio data and non-compressed audio data stored thereon can be playedback without changing the medium.

In the playback apparatus according to the present invention, if thepredetermined medium received in the playback apparatus includes asession formed of a lead-in, a data storage area, and a lead-out, thedetermining unit may recognize that non-compressed audio data and datain another format are stored in the data storage area in the session,and may recognize that compressed audio data is contained in the data inanother format, thereby determining that both non-compressed audio dataand compressed audio data are stored in the predetermined medium.

In the playback apparatus according to the present invention, thedetermining unit may recognize whether or not a plurality of sessionsare included in the predetermined medium, and may recognize thatcompressed audio data is contained in at least one session of theplurality of sessions, thereby determining that both non-compressedaudio data and compressed audio data are stored in the predeterminedmedium.

The present invention further provides a method for playing back, on aplayback apparatus, a medium having audio data stored thereon, whereinit is determined whether a medium received by the playback apparatusstores one or both of non-compressed audio data and compressed audiodata; and the audio data stored on the received medium is played backaccording to the determination result. In the playback method accordingto the present invention, if it is determined that the received mediumstores both non-compressed audio data and compressed audio data, onedata of the non-compressed audio data and the compressed audio data isplayed back, and the other data is subsequently played back in asequential manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of an audio deviceaccording the present embodiment.

FIG. 2 is a flowchart showing a playback routine for the audio deviceaccording to the present embodiment.

FIG. 3 is a flowchart showing a playback routine for the audio deviceaccording to the present embodiment.

FIG. 4 is a diagram showing the file structure of a CD-DA.

FIG. 5 is a diagram showing the file structure of a CD-ROM.

FIG. 6 is a diagram showing the file structure of a Mixed-mode CD.

FIG. 7 is a diagram showing the file structure of an Enhanced CD.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described hereinbelow with respect to anembodiment.

FIG. 1 is a block diagram showing the system configuration of an audiodevice 10 according to the present embodiment.

The audio device 10 is formed of a mecha-deck unit 11, a mainmicrocomputer 12, a display unit 13, an operation key 14, a power supply15, an amp 16, and a speaker 17.

The mecha-deck unit 11 is formed of a spindle motor 2 which drives adisk 1 to rotate, a pickup 3 for reading data on the disk 1, an RF(Radio Frequency) amp 4, a motor driver 5, a CD DSP (Digital SignalProcessor) & servo 6, a microcomputer 7, a decoder 8 comprising a CD-ROMdecoder unit and a compressed audio data decoder unit, and a DAC (D/Aconverter) 9.

The main microcomputer 12 supervises the overall control of the audiodevice 10. The display unit 13 and the operation key 14 are connected tothe main microcomputer 12. When the operation key 14 corresponding tothe operation desired by a user is operated, the main microcomputer 12instructs the microcomputer 7 of the mecha-deck unit 11 to perform thatoperation. The display unit 13 displays the operation state of the audiodevice 10, and others.

The operation to play back audio data recorded on the disk 1 on the thusconstructed audio device 10 is now described. The audio device 10 hastwo modes, as selections for audio data playback modes, namely, a modefor playing back CD-DA non-compressed audio data, and a mode for playingback MP3 etc. compressed audio data, and may select one of them. It isnoted that what is simply called audio data collectively refers tocompressed audio data and non-compressed audio data. Although MP3 isdescribed as compressed audio data by way of example in the presentembodiment, it goes without saying that other formats of compressedaudio data, such as ATRAC3 and WMA described above, may also be used.

First, a playback mode for CD-DA non-compressed audio data is described.This playback mode can function if the disk 1 is one of a CD-DA disk, aMixed-mode CD, and an Enhanced CD.

The motor driver 5 causes the spindle motor 2 having the disk 1 loadedthereon to rotate. The pickup 3 reads CD-DA audio data from the disk 1which is rotating. The CD-DA audio data read from the pickup 3 isamplified by the RF amp 4, and is demodulated by the CD DSP & servo 6.The signal demodulated by the CD DSP & servo 6 is applied to the DAC 9through the decoder 8. That signal merely passes through the decoder 8.The DAC 9 which has received the signal demodulated by the CD DSP &servo 6 converts that signal into an audio signal, and outputs theresult to the amp 16. The audio signal amplified by the amp 16 is playedback through the speaker 17. The above-described series of processes iscontrolled by the microcomputer 7 according to instructions from themain microcomputer 12.

Then, a playback mode for MP3 etc. compressed audio data is described.This playback mode can function if the disk 1 is one of a CD-ROM disk, aMixed-mode CD, and an Enhanced CD.

The motor driver 5 causes the spindle motor 2 having the disk 1 loadedthereon to rotate. The pickup 3 reads audio data in the CD-ROM format,that is, as computer data, from the disk 1 which is rotating. The audiodata read from the pickup 3 is amplified by the RF amp 4, and isdemodulated by the CD DSP & servo 6. The operation up to now is the sameas that for playback of CD-DA non-compressed audio data. The signaldemodulated by the CD DSP & servo 6 is passed to the CD-ROM decoder unitin the decoder 8, where the data is demodulated into CD-ROM format, fromwhich MP3 etc. audio data, that is, compressed audio data, is extracted.The extracted compressed audio data is demodulated into CD-DA audio databy the compressed audio decoder unit in the decoder 8. The CD-DA audiodata is converted into an audio signal by the DAC 9, and the result isoutput to the amp 16. The audio signal amplified by the amp 16 is playedback through the speaker 17. The above-described series of processes iscontrolled by the microcomputer 7 according to instructions from themain microcomputer 12.

While a playback mode for CD-DA non-compressed audio data and a playbackmode for MP3 etc. compressed audio data have been separately described,the audio device 10 according to the present embodiment can analyze theformat of the disk 1 to select a playback mode according to the analysisresult. This analysis is based on recognizing whether the disk 1 is ofthe CD-DA, CD-ROM, Mixed-mode CD, or Enhanced CD format, or any otherformat CD.

The file structure of the disk 1 in various formats is now described.FIG. 4 shows the file structure of the disk 1 in the CD-DA format. InCD-DA, a lead-in, a CD-DA track, and a lead-out are sequentiallyarranged from the inner circumference of the disk 1. One unit startingwith the lead-in and ending with the lead-out is referred herein to as asession. The published standards for CD-DA, the “Red Book,” specifiesthat a CD-DA has only one session. A CD-DA track contains a single or aplurality of songs. The songs are written as non-compressed audio data.The lead-in contains a TOC (Table Of Contents). The TOC containsinformation in the CD-DA track, that is, information about the starttime of each track (each song) and information indicating that the datain the data storage area (the CD-DA track in this case) is CD-DA audiodata. The TOC also contains information indicating a single or aplurality of sessions. A TOC in disks of other formats contains the sameinformation.

Next, FIG. 5 shows the file structure of the disk 1 in the CD-ROMformat. The specification of the CD-ROM is defined in the “Yellow Book”as a medium which is an extension of the CD-DA developed for music andwhich stores computer-manipulated data. In CD-ROM, a lead-in, a PVD(Primary Volume Descriptor), a path table, a data track, and a lead-outare sequentially arranged from the inner circumference of the disk 1.Similarly to CD-DA, a session represents one unit starting with thelead-in and ending with the lead-out. The lead-in contains a TOC, andthe TOC is referred to, thereby recognizing if computer data is storedin the data track. The data track contains a single or a plurality ofsongs. The songs are written as compressed audio data, for example, MP3.The compressed audio data has a computer data format. By referring tothe PVD and the path table, the presence of compressed audio data can bechecked. For example, if an extension “mp3” is added to the file name ofMP3 compressed audio data, the information about that extension can beconfirmed by referring to the PVD and the path table. Computer dataother than compressed audio data may also be written on the data track.

FIG. 6 shows the file structure of a Mixed-mode CD. As previouslydescribed, the Mixed-mode CD stores a data track and an audio track in asingle medium. That is, in the Mixed-mode CD, a lead-in, a PVD, a pathtable, a data track, a CD-DA track, and a lead-out are sequentiallyarranged from the inner circumference of the disk 1. The data trackcontains a single or a plurality of songs. These songs are written ascompressed audio data, for example, MP3. The CD-DA track contains asingle or a plurality of songs. The songs are written as non-compressedaudio data. Therefore, the Mixed-mode CD serves as a music medium havinga mixture of compressed audio data and non-compressed audio data.Similarly to the CD-ROM format, computer data other than compressedaudio data can be written on the data track.

FIG. 7 shows the file structure of an Enhanced CD. As described above,the Enhanced CD has two sessions in a single medium, and thespecification thereof is defined in the “Blue Book”. In the Enhanced CD,a first lead-in, a CD-DA track, a first lead-out, a second lead-in, aPVD, a path table, a data track, and a second lead-out are sequentiallyarranged from the inner circumference of the disk 1. Similarly to theMixed-mode CD, compressed audio data can be written on the data track,and non-compressed audio data can be written on the CD-DA track.Therefore, the Enhanced CD serves as a music medium having a mixture ofcompressed audio data and non-compressed audio data. The differencebetween the Enhanced CD and the Mixed-mode CD is that the Mixed-mode CDhas only one session, whilst the Enhanced CD has two sessions, namely,the first session and the second session. In addition, the Mixed-mode CDhas the data track and the CD-DA track, which exist in a single session,whilst the Enhanced CD has only either the data track or the CD-DAtrack, which exists in a single session.

Since a CD-DA, a CD-ROM, a Mixed-mode CD, and an Enhanced CD aredifferent in file structure as described above, by referring to the filestructure the format of the predetermined disk 1 can be determined.

In the following description, a routine for analyzing the disk format ofthe disk 1 which is loaded on the audio device 10 and for playing backaudio data based on the analysis result is described with reference tothe flowcharts shown in FIGS. 2 and 3. The routine in the flowchartsshown in FIGS. 2 and 3 is executed by a program installed in themicrocomputer 7 in the mecha-deck unit 11.

FIGS. 2 and 3 show a series of processes in the audio device 10, inwhich FIG. 2 shows a routine when the disk 1 is of the CD-ROM format orMixed-mode CD, and FIG. 3 shows a routine when the disk 1 is of theCD-DA format, the Enhanced CD format, or other formats.

When a user uses the operation key 14 to request to play back the disk1, the TOC (Table Of Contents) in the lead-in is referred to through thepickup 3 (S101). In the storage disk of this type, it is defined thatthe lead-in on the inner circumference of the disk be accessed first.Therefore, in the case of an Enhanced CD including two sessions, the TOCin the first session should be referred to.

By referring to the TOC, it is determined whether or not all the tracksin the disk 1 are in the CD-DA format (S102). If all the tracks compriseCD-DA data, the routine proceeds to S110 shown in FIG. 3. The routinesubsequent to S110 is described later.

If it is determined in S102 that all the tracks are not in the CD-DAformat, then, in S103, it is determined whether or not all the trackscomprise data. The data as referred to herein means computer data, anddoes not include CD-DA audio data. If all the tracks comprise data, itis recognized that the disk 1 is a disk of the CD-ROM format (S108). Inother words, it is determined that it is a medium having only compressedaudio data stored thereon as audio data. Then, the audio device 10selects a compressed audio data playback mode to play back thecompressed audio data in the data track (S109).

If it is determined in S103 that all the tracks do not comprise data, itcan be recognized that the disk 1 is a medium having a mixture of thedata track and the CD-DA track in a single session since it isdetermined in S102 that all the tracks do not comprise CD-DA. That is,it is determined that the disk 1 is a Mixed-mode CD (S104).

Even if the disk 1 is a Mixed-mode CD, compressed audio data is notnecessarily present in its data track. Then, it is determined whether ornot compressed audio data is present in the data track (S105). Thisdetermination can be performed by referring to the PVD and the pathtable to find the presence or absence of an extension indicatingcompressed audio data. As described above, if an MP3 extension is, forexample, “mp3”, by finding the extension “mp3,” it can be recognized ifcompressed audio data is present in the data track. Consequently, itshould be determined that the disk 1 is a medium having a mixture ofcompressed audio data and non-compressed audio data.

If compressed audio data is present, the audio device 10 selects acompressed audio data playback mode to play back the compressed audiodata in the data track (S106). After playing back the compressed audiodata in the data track, the audio device 10 selects a non-compressedaudio data playback mode to play back the non-compressed audio data inthe CD-DA track (S107).

If, on the other hand, it is determined in S105 that compressed audiodata is not present in the data track, the audio device 10 selects anon-compressed audio data playback mode to play back the non-compressedaudio data in the CD-DA track (S107).

Next, the routine subsequent to S110 is described with reference to FIG.3. The routine subsequent to S110 corresponds to a routine when it isdetermined in S102 that all the tracks have CD-DA audio data storedtherein.

If it is determined in S102 that all the tracks have CD-DA audio datastored therein, it is determined whether or not a second session existsin the disk 1 (S110). The presence or absence of the second session canbe determined based on the information in the TOC. If it is determinedthat no second session exists, it should be determined that the disk 1is a disk of the CD-DA format (S117) since the disk 1 has a singlesession and it is determined in S102 that CD-DA audio data is stored inall the tracks in the session. If it is determined that it is a disk ofthe CD-DA format, the audio device 10 selects a non-compressed audiodata playback mode to play back the non-compressed audio data in theCD-DA track (S118).

If it is determined in S110 that a second session exists, a secondlead-in is read (S111). The TOC in the second lead-in is referred to todetermine whether or not the track in the second session is a data track(S112). If it is determined that the track in the second session is adata track, it is then determined that the disk 1 is an Enhanced CD(S113) since a CD-DA track is present in the first session. If, on theother hand, the track in the second session is not a data track, it isdetermined that it is a disk in another format (S119).

If it is determined in S113 that it is an Enhanced CD, the audio device10 selects a non-compressed audio data playback mode to play back thenon-compressed audio data in the CD-DA track (the first session) (S114).Then, after playback of the non-compressed audio data in the CD-DA trackis completed, it is determined whether or not compressed audio data ispresent in the data track in the second session (S115). The technique todetermine whether or not compressed audio data is present is the same asin S105. If compressed audio data is present, the audio device 10selects a compressed audio data playback mode to play back thecompressed audio data in the data track (the second session) (S116).After playback of the compressed audio data in the data track iscompleted, or if compressed audio data is not present, the routine ends.

As described above, the audio device 10 according to the presentembodiment can play back the disk 1 having a mixture of CD-DAnon-compressed audio data and compressed audio data. Whilenon-compressed audio data has a large storage volume and superior soundquality, compressed audio data has slightly poorer sound quality, buthas a small storage volume. A user should store songs sensitive to soundquality as CD-DA non-compressed audio data, and store songs insensitiveto sound quality, such as background music, as MP3 etc. compressed audiodata. When such a disk 1 is played back on the audio device 10, the userdoes not have to be nervous about a mixture of non-compressed audio dataand compressed audio data.

The above-described embodiment is merely one form of the presentinvention. For example, after a Mixed-mode CD is determined in S104, thecompressed audio data is played back after which the CD-DAnon-compressed audio data is played back; however, the playback may bereordered so that the non-compressed audio data is played back afterwhich the compressed audio data is played back. Also after an EnhancedCD is determined in S113, the CD-DA non-compressed audio data is playedback after which the compressed audio data is played back; however,after the determination in S115, that is, after it is determined whetheror not compressed audio data is present in the track in the secondsession, the series of playback processes may be performed.

In the foregoing embodiment, after a Mixed-mode CD is determined, andplayback for all compressed audio data is completed, non-compressedaudio data is played back; however, compressed audio data andnon-compressed audio data may be alternately played back. Moreover,after a Mixed-mode CD is determined, song names corresponding to thedata stored in the data track and the CD-DA track may be presented onthe display 13 to play a user selected song. The same as the playbacktechnique is true for an Enhanced CD.

A variety of other modifications may be made without departing from thespirit and scope of the present invention, in which the format of thedisk 1 is analyzed and compressed audio data and non-compressed audiodata, which are mixed in the single disk 1, are played back according tothis analysis result.

As described above, according to the present invention, an audio datastorage medium having a mixture of compressed audio data andnon-compressed audio data is provided, thus allowing a user to enjoymusic on a single disk having many songs sensitive to sound quality andsongs insensitive to sound quality stored thereon. According to thepresent invention, furthermore, without having to change a disk, a usercan enjoy music on an audio data storage medium having a mixture ofcompressed audio data and non-compressed audio data.

1. A playback apparatus for playing back a medium having audio datastored thereon, comprising: a recognition unit configured to recognize asession of the medium, wherein each session includes a lead-in area, adata storage area, and a lead-out area; a determining unit configured todetermine that the medium received therein contains a mixture ofcompressed audio data and non-compressed audio data in the data storagearea of each session; and a playback mechanism configured to play backthe compressed audio data and the non-compressed audio data stored inthe medium based on results of both the determining unit and recognitionunit, the playback mechanism reproducing the compressed audio databefore the non-compressed audio data when only one session is recognizedby the recognition unit, and reproducing the non-compressed audio databefore the compressed audio data when two sessions are recognized by therecognition unit.
 2. The playback apparatus according to claim 1,wherein the medium includes at least two sessions each including alead-in area a data storage area, and a lead-out area, and thedetermining unit is further configured to determine that compressedaudio data is stored in the data storage area in at least one session ofthe at least two sessions and non-compressed audio data is stored in thedata storage area in another session of the at least two sessions. 3.The playback apparatus according to claim 1, wherein the determiningunit is further configured to determine whether one of compressed audiodata or non-compressed audio data is stored in the data storage area inthe session.
 4. A method for playing back, on a playback apparatus, amedium, the method comprising: recognizing a session of the medium,wherein each session includes a lead-in area, a data storage area, and alead-out area; determining the medium contains a mixture of compressedaudio data and non-compressed audio data in the data storage area ofeach session; and reproducing the compressed audio data andnon-compressed audio data stored in the medium based on results of boththe determining and recognizing, the reproducing reproduces thecompressed audio data before the non-compressed audio data when only onesession is recognized, and reproduces the non-compressed audio databefore the compressed audio data when two sessions are recognized.
 5. Aplayback apparatus for playing back a medium having audio data storedthereon, comprising: a means for recognizing a session of the medium,wherein each session includes a lead-in area, a data storage area, and alead-out area; a means for determining that the medium received thereincontains a mixture of compressed audio data and non-compressed audiodata in the data storage area of each session; and a means forreproducing the compressed audio data and the non-compressed audiostored in the medium based on results of both the means for recognizingand means for determining, the means for reproducing reproduces thecompressed audio data before the non-compressed audio data when only onesession is recognized by the means for recognizing, and reproduces thenon-compressed audio data before the compressed audio data when twosessions are recognized by the means for recognizing.